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https://www.readbyqxmd.com/read/27917245/reactivity-of-a-ruthenium-carbonyl-complex-in-the-methanol-dehydrogenation-reaction
#1
Fenna F van de Watering, Martin Lutz, Wojciech I Dzik, Bas de Bruin, Joost N H Reek
Finding new catalysts for the release of molecular hydrogen from methanol is of high relevance in the context of the development of sustainable energy carriers. Herein, we report that the ruthenium complex Ru(salbinapht)(CO)(Pi-Pr3) {salbinapht=2-[({2'-[(2-hydroxybenzyl)amino]-[1,1'-binaphthalen]-2-yl}imino)methyl]phenolato} (2) catalyzes the methanol dehydrogenation reaction in the presence of base and water to yield H2, formate, and carbonate. Dihydrogen is the only gas detected and a turnover frequency up to 55 h(-1) at 82 °C is reached...
September 7, 2016: ChemCatChem
https://www.readbyqxmd.com/read/27867424/aldehyde-and-ketone-synthesis-by-p450-catalyzed-oxidative-deamination-of-alkyl-azides
#2
Simone Giovani, Hanan Alwaseem, Rudi Fasan
Heme-containing proteins have recently attracted increasing attention for their ability to promote synthetically valuable transformations not found in nature. Following the recent discovery that engineered variants of myoglobin can catalyze the direct conversion of organic azides to aldehydes, we investigated the azide oxidative deamination reactivity of a variety of hemoproteins featuring different heme coordination environments. Our studies show that although several heme-containing enzymes possess basal activity in this reaction, an engineered variant of the bacterial cytochrome P450 CYP102A1 constitutes a particularly efficient biocatalyst for promoting this transformation, exhibiting a broad substrate scope along with high catalytic activity (up to 11,300 TON), excellent chemoselectivity, and enhanced reactivity toward secondary alkyl azides to yield ketones...
August 22, 2016: ChemCatChem
https://www.readbyqxmd.com/read/27840663/a-dft-study-of-co2-hydrogenation-on-faujasite-supported-ir4-clusters-on-the-role-of-water-for-selectivity-control
#3
Bartłomiej M Szyja, Daniel Smykowski, Jerzy Szczygieł, Emiel J M Hensen, Evgeny A Pidko
Reaction mechanisms for the catalytic hydrogenation of CO2 by faujasite-supported Ir4 clusters were studied by periodic DFT calculations. The reaction can proceed through two alternative paths. The thermodynamically favoured path results in the reduction of CO2 to CO, whereas the other, kinetically preferred channel involves CO2 hydrogenation to formic acid under water-free conditions. Both paths are promoted by catalytic amounts of water confined inside the zeolite micropores with a stronger promotion effect for the reduction path...
August 8, 2016: ChemCatChem
https://www.readbyqxmd.com/read/27840662/copper-i-phosphinite-complexes-in-click-cycloadditions-three-component-reactions-and-preparation-of-5-iodotriazoles
#4
Juana M Pérez, Peter Crosbie, Steven Lal, Silvia Díez-González
The remarkable activity displayed by copper(I)-phosphinite complexes of general formula [CuBr(L)] in two challenging cycloadditions is reported: a) the one-pot azidonation/cycloaddition of boronic acids, NaN3, and terminal alkynes; b) the cycloaddition of azides and iodoalkynes. These air-stable catalysts led to very good results in both cases and the expected triazoles could be isolated in pure form under 'Click-suitable' conditions.
July 6, 2016: ChemCatChem
https://www.readbyqxmd.com/read/27840661/real-time-analysis-of-a-working-triethylaluminium-modified-cr-ti-sio2-ethylene-polymerization-catalyst-with-in%C3%A2-situ-infrared-spectroscopy
#5
Dimitrije Cicmil, Jurjen Meeuwissen, Aurélien Vantomme, Bert M Weckhuysen
A diffuse reflectance infrared Fourier-transform (DRIFT) study has been conducted at 373 K and 1 bar on an industrial Cr/Ti/SiO2 Phillips-type catalyst modified with, and without, triethylaluminium (TEAl) as co-catalyst. The reaction rate of the polymerization of ethylene, as monitored by the increase in the methylene stretching band of the growing polyethylene (PE), has been investigated as a function of the titanium content. After an initial period of mixed kinetics, with the reaction rate significantly higher for the TEAl-modified catalysts compared with the non-modified catalysts, the polymerization proceeded as a pseudo-zero-order reaction with a reaction rate that increased as a function of titanium loading...
June 7, 2016: ChemCatChem
https://www.readbyqxmd.com/read/27812371/combined-operando-x-ray-diffraction-raman-spectroscopy-of-catalytic-solids-in-the-laboratory-the-co-tio2-fischer-tropsch-synthesis-catalyst-showcase
#6
Korneel H Cats, Bert M Weckhuysen
A novel laboratory setup for combined operando X-ray diffraction and Raman spectroscopy of catalytic solids with online product analysis by gas chromatography is presented. The setup can be used with a laboratory-based X-ray source, which results in important advantages in terms of time-on-stream that can be measured, compared to synchrotron-based experiments. The data quality was much improved by the use of a relatively high-energy MoKα radiation instead of the more conventional CuKα radiation. We have applied the instrument to study the long-term deactivation of Co/TiO2 Fischer-Tropsch synthesis (FTS) catalysts...
April 20, 2016: ChemCatChem
https://www.readbyqxmd.com/read/26925172/improved-efficiency-for-partial-oxidation-of-methane-by-controlled-copper-deposition-on-surface-modified-zsm-5
#7
Thomas Sheppard, Helen Daly, Alex Goguet, Jillian M Thompson
The mono(μ-oxo) dicopper cores present in the pores of Cu-ZSM-5 are active for the partial oxidation of methane to methanol. However, copper on the external surface reduces the ratio of active, selective sites to unselective sites. More efficient catalysts are obtained by controlling the copper deposition during synthesis. Herein, the external exchange sites of ZSM-5 samples were passivated by bis(trimethylsilyl) trifluoroacetamide (BSTFA) followed by calcination, promoting selective deposition of intraporous copper during aqueous copper ion exchange...
February 2016: ChemCatChem
https://www.readbyqxmd.com/read/27134687/diarylmethanes-through-an-unprecedented-palladium-catalyzed-c-c-cross-coupling-of-1-aryl-methoxy-1-h-benzotriazoles-with-arylboronic-acids
#8
Manish K Singh, Mahesh K Lakshman
1-(Aryl)methoxy-1H-benzotriazoles (ArCH2OBt) are bench-stable reagents that are prepared readily from 1H-benzotriazol-1-yl-4-methylbenzenesulfonate (BtOTs) and benzylic alcohols. These compounds, which contain a N-O-C bond, undergo cross-coupling with arylboronic acids by C-O bond scission with catalysts that comprise Pd(OAc)2 and biarylphosphine ligands. Such reactivity of ArCH2OBt derivatives, leading to diarylmethanes, has not been described previously and constitutes a new activation of benzylic alcohols...
December 14, 2015: ChemCatChem
https://www.readbyqxmd.com/read/26697122/noninvasive-nanoscopy-uncovers-the-impact-of-the-hierarchical-porous-structure-on-the-catalytic-activity-of-single-dealuminated-mordenite-crystals
#9
Alexey V Kubarev, Kris P F Janssen, Maarten B J Roeffaers
Spatial restrictions around catalytic sites, provided by molecular-sized micropores, are beneficial to reaction selectivity but also inherently limit diffusion. The molecular transport can be enhanced by introducing meso- and macropores. However, the impact of this extraframework porosity on the local nanoscale reactivity is relatively unexplored. Herein we show that the area of enhanced reactivity in hierarchical zeolite, examined with super-resolution fluorescence microscopy, is spatially restricted to narrow zones around meso- and macropores, as observed with focused ion-beam-assisted scanning electron microscopy...
November 2015: ChemCatChem
https://www.readbyqxmd.com/read/26613011/x-ray-fluorescence-tomography-of-aged-fluid-catalytic-cracking-catalyst-particles-reveals-insight-into-metal-deposition-processes
#10
Sam Kalirai, Ulrike Boesenberg, Gerald Falkenberg, Florian Meirer, Bert M Weckhuysen
Microprobe X-ray fluorescence tomography was used to investigate metal poison deposition in individual, intact and industrially deactivated fluid catalytic cracking (FCC) particles at two differing catalytic life-stages. 3 D multi-element imaging, at submicron resolution was achieved by using a large-array Maia fluorescence detector. Our results show that Fe, Ni and Ca have significant concentration at the exterior of the FCC catalyst particle and are highly co-localized. As concentrations increase as a function of catalytic life-stage, the deposition profiles of Fe, Ni, and Ca do not change significantly...
November 2015: ChemCatChem
https://www.readbyqxmd.com/read/26613010/surface-segregation-of-fe-in-pt-fe-alloy-nanoparticles-its-precedence-and-effect-on-the-ordered-phase-evolution-during-thermal-annealing
#11
Sagar Prabhudev, Matthieu Bugnet, Guo-Zhen Zhu, Christina Bock, Gianluigi A Botton
Coupling electron microscopy techniques with in situ heating ability allows us to study phase transformations on the single-nanoparticle level. We exploit this setup to study disorder-to-order transformation of Pt-Fe alloy nanoparticles, a material that is of great interest to fuel-cell electrocatalysis and ultrahigh density information storage. In contrast to earlier reports, we show that Fe (instead of Pt) segregates towards the particle surface during annealing and forms a Fe-rich FeO x outer shell over the alloy core...
November 2015: ChemCatChem
https://www.readbyqxmd.com/read/26613009/enzyme-modified-particles-for-selective-biocatalytic-hydrogenation-by-hydrogen-driven-nadh-recycling
#12
Holly A Reeve, Lars Lauterbach, Oliver Lenz, Kylie A Vincent
We describe a new approach to selective H2-driven hydrogenation that exploits a sequence of enzymes immobilised on carbon particles. We used a catalyst system that comprised alcohol dehydrogenase, hydrogenase and an NAD(+) reductase on carbon black to demonstrate a greater than 98 % conversion of acetophenone to phenylethanol. Oxidation of H2 by the hydrogenase provides electrons through the carbon for NAD(+) reduction to recycle the NADH cofactor required by the alcohol dehydrogenase. This biocatalytic system operates over the pH range 6-8 or in un-buffered water, and can function at low concentrations of the cofactor (10 μm NAD(+)) and at H2 partial pressures below 1 bar...
November 2015: ChemCatChem
https://www.readbyqxmd.com/read/26583051/identification-of-active-and-spectator-sn-sites-in-sn-%C3%AE-following-solid-state-stannation-and-consequences-for-lewis-acid-catalysis
#13
Ceri Hammond, Daniele Padovan, Abbas Al-Nayili, Peter P Wells, Emma K Gibson, Nikolaos Dimitratos
Lewis acidic zeolites are rapidly emerging liquid-phase Lewis acid catalysts. Nevertheless, their inefficient synthesis procedure currently prohibits greater utilization and exploitation of these promising materials. Herein, we demonstrate that Sn(IV)-containing zeolite beta can readily be prepared both selectively and extremely rapidly by solid-state incorporation (SSI) method. Through a combination of spectroscopic (XRD, UV/Vis, X-ray absorption, magic-angle spinning NMR, and diffuse reflectance infrared Fourier transform spectroscopy) studies, we unambiguously demonstrate that site-isolated, isomorphously substituted Sn(IV) sites dominate the Sn population up to a loading of 5 wt % Sn...
October 2015: ChemCatChem
https://www.readbyqxmd.com/read/26583050/amination-of-%C3%AF-functionalized-aliphatic-primary-alcohols-by-a-biocatalytic-oxidation-transamination-cascade
#14
Mathias Pickl, Michael Fuchs, Silvia M Glueck, Kurt Faber
Amination of non-activated aliphatic fatty alcohols to the corresponding primary amines was achieved through a five-enzyme cascade reaction by coupling a long-chain alcohol oxidase from Aspergillus fumigatus (LCAO_Af) with a ω-transaminase from Chromobacterium violaceum (ω-TA_Cv). The alcohol was oxidized at the expense of molecular oxygen to yield the corresponding aldehyde, which was subsequently aminated by the PLP-dependent ω-TA to yield the final primary amine product. The overall cascade was optimized with respect to pH, O2 pressure, substrate concentration, decomposition of H2O2 (derived from alcohol oxidation), NADH regeneration, and biocatalyst ratio...
October 2015: ChemCatChem
https://www.readbyqxmd.com/read/26251674/chemoenzymatic-synthesis-of-ortho-meta-and-para-substituted-derivatives-of-l-threo-3-benzyloxyaspartate-an-important-glutamate-transporter-blocker
#15
Jandré de Villiers, Marianne de Villiers, Edzard M Geertsema, Hans Raj, Gerrit J Poelarends
A simple, three-step chemoenzymatic synthesis of l-threo-3-benzyloxyaspartate (l-TBOA), as well as l-TBOA derivatives with F, CF3, and CH3 substituents at the aromatic ring, starting from dimethyl acetylenedicarboxylate was investigated. These chiral amino acids, which are extremely difficult to prepare by chemical synthesis, form an important class of inhibitors of excitatory amino acid transporters involved in the regulation of glutamatergic neurotransmission. In addition, a new chemical procedure for the synthesis of racemic mixtures of TBOA and its derivatives was explored...
July 3, 2015: ChemCatChem
https://www.readbyqxmd.com/read/27158274/binder-effects-in-sio2-and-al2o3-bound-zeolite-zsm-5-based-extrudates-as-studied-by-microspectroscopy
#16
Gareth T Whiting, Florian Meirer, Machteld M Mertens, Anton-Jan Bons, Brian M Weiss, Paul A Stevens, Emiel de Smit, Bert M Weckhuysen
Microspectroscopic methods were explored to investigate binder effects occurring in ZSM-5-containing SiO2- and Al2O3-bound millimetre-sized extrudates. Using thiophene as a selective probe for Brønsted acidity, coupled with time-resolved in situ UV/Vis and confocal fluorescence microspectroscopy, variations in reactivity and selectivity between the two distinct binder types were established. It was found that aluminium migration occurs in ZSM-5-containing Al2O3-bound extrudates, forming additional Brønsted acid sites...
April 20, 2015: ChemCatChem
https://www.readbyqxmd.com/read/26925171/immobilization-of-phenylalanine-ammonia-lyase-on-single-walled-carbon-nanotubes-for-stereoselective-biotransformations-in-batch-and-continuous-flow-modes
#17
Judith H Bartha-Vári, Monica I Toşa, Florin-Dan Irimie, Diána Weiser, Zoltán Boros, Beáta G Vértessy, Csaba Paizs, László Poppe
Carboxylated single-walled carbon nanotubes (SwCNTCOOH) were used as a support for the covalent immobilization of phenylalanine ammonia-lyase (PAL) from parsley by two different methods. The nanostructured biocatalysts (SwCNTCOOH-PAL(I) and SwCNTCOOH-PAL(II)) with low diffusional limitation were tested in the batch-mode kinetic resolution of racemic 2-amino-3-(thiophen-2-yl)propanoic acid (1) to yield a mixture of (R)-1 and (E)-3-(thiophen-2-yl)acrylic acid (2) and in ammonia addition to 2 to yield enantiopure (S)-1...
April 7, 2015: ChemCatChem
https://www.readbyqxmd.com/read/26413174/highly-effective-pt-based-water-gas-shift-catalysts-by-surface-modification-with-alkali-hydroxide-salts
#18
Matthias Kusche, Karen Bustillo, Friederike Agel, Peter Wasserscheid
Herein, we describe an economical and convenient method to improve the performance of Pt/alumina catalysts for the water-gas shift reaction through surface modification of the catalysts with alkali hydroxides according to the solid catalyst with ionic liquid layer approach. The results are in agreement with our findings reported earlier for methanol steam reforming. This report indicates that alkali doping of the catalyst plays an important role in the observed catalyst activation. In addition, the basic and hygroscopic nature of the salt coating contributes to a significant improvement in the performance of the catalyst...
March 2015: ChemCatChem
https://www.readbyqxmd.com/read/26113881/direct-electrochemical-addressing-of-immobilized-alcohol-dehydrogenase-for-the-heterogeneous-bioelectrocatalytic-reduction-of-butyraldehyde-to-butanol
#19
S Schlager, H Neugebauer, M Haberbauer, G Hinterberger, N S Sariciftci
Modified electrodes using immobilized alcohol dehydrogenase enzymes for the efficient electroreduction of butyraldehyde to butanol are presented as an important step for the utilization of CO2-reduction products. Alcohol dehydrogenase was immobilized, embedded in an alginate-silicate hybrid gel, on a carbon felt (CF) electrode. The application of this enzyme to the reduction of an aldehyde to an alcohol with the aid of the coenzyme nicotinamide adenine dinucleotide (NADH), in analogy to the final step in the natural reduction cascade of CO2 to alcohol, has been already reported...
March 2015: ChemCatChem
https://www.readbyqxmd.com/read/25937846/catalytic-properties-of-unsupported-palladium-nanoparticle-surfaces-capped-with-small-organic-ligands
#20
Diego J Gavia, Young-Seok Shon
This Minireview summarizes a variety of intriguing catalytic studies accomplished by employing unsupported, either solubilized or freely mobilized, and small organic ligand-capped palladium nanoparticles as catalysts. Small organic ligands are gaining more attention as nanoparticle stabilizers and alternates to larger organic supports, such as polymers and dendrimers, owing to their tremendous potential for a well-defined system with spatial control in surrounding environments of reactive surfaces. The nanoparticle catalysts are grouped depending on the type of surface stabilizers with reactive head groups, which include thiolate, phosphine, amine, and alkyl azide...
March 1, 2015: ChemCatChem
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